Preparation Of Doped Carbon Materials And Its Application Of Supercapacitors

Supercapacitors,as an energy storage device,have the advantages of high power density,excellent reversibility and long cycle life,and are widely used in various fields such as power cars,personal electronic products.In general,a supercapacitor device consists of an active material electrode,a porous membrane,and an electrolyte.The electrode material is a key factor of the capacitor.The quality of the electrode material directly affect the electrochemical performance of the supercapacitor.However,most commercially available electrode materials are porous carbon materials,but their application is limited due to their lower energy density.Therefore,in order to meet people’s eager demand for energy in the future,it will increase its energy density without affecting the other properties of carbon materials.From the energy density calculation formula,we can know that the energy density of the carbon-based electrode material can be increased by increasing the voltage or specific capacity across the capacitor.Therefore,this dissertation focuses on improving the specific capacitance of the material by doping the carbon material with a heteroatom to increase the energy density of the supercapacitor.The main research contents and results are as follows:（1）nitrogen-doped carbon material with high specific surface and high nitrogen content is prepared using a chemical agent ZnCl₂ as a pore former and a dehydrating agent,benzotriazole（BTA）as precursor.The structure and electrochemical properties of the material are controlled by controlling the activation temperature and the mass ratio of ZnCl₂to BTA.The structure,morphology and pore structure of the material were characterized by SEM,TEM,XPS,XRD and BET,and the electrochemical test results were used to further optimize the preparation conditions so as to obtain the optimal material.The test results show that when the heat treatment temperature is 700°C and the mass ratio of ZnCl₂ to BTA is 2,the nitrogen content of the sample NC-2-700 is 10.27 wt%,and its specific surface area is 1228 m²·g^-1;in the three-electrode system test,the specific capacitance is 332 F·g^-1 at a current density of 0.5 A·g^-1;in a two-electrode system test,the energy density and power density of the symmetrical carbon-based capacitor is 12.94 Wh kg^-1 and 375 W kg^-1 at a current density of 1 A·g^-1,respectively.even at current densities of 10 A·g^-1,the energy density and power density remain 5.43 Wh kg^-1 and 3750 W kg^-1,respectively.Therefore,the nitrogen-rich N-doped porous material with high specific surface has a very good application prospect in supercapacitors.（2）a combination of chemical activation method and in-situ nitrogen doping method was applied in this article.And N/P/O-ternary Doped porous carbon material was synthesized by using benzotriazole（BTA）as a carbon source and a nitrogen source as well as H₃PO₄ as dopant and an activator.SEM,TEM,XPS,XRD,and BET were used to characterize the microstructure and surface elements of the doped carbon materials.Then the experimental conditions were optimized by combining the results of the electrochemical tests to obtain the best performance materials.The experimental results show that the PNOC-3-700 sample has a high specific capacity(227.9 F·g^-1 at 1 A·g^-1)and a high energy density(17.80 Wh kg^-1),even at 10 A·g^-1,its energy density is still 12.51 W h kg^-1,which is due to its high specific surface area(1337.7 m²·g^-1)and abundant heteroatoms or functional groups（O:11.4 at%,N:6.5 at%,P:1.1 at%）,especially N-5,N-6,and oxygen-containing functional groups（quinone,C=O,-O-,-COOH and-OH）.